## Humidification

### 0600-6-mt-1mark

0600-6-mt

If the temperature of atmosphere increases at constant absolute humidity, the percentage saturation would

• decrease

• remain constant

• increase

• none of these

### 0600-7-mt-1mark

0600-7-mt

If the temperature of atmosphere increases at constant absolute humidity, the wet-bulb temperature would

• decrease

• remain constant

• increase

• none of these

### GATE-CH-1988-5-b-vi-mt-2mark

1988-5-b-vi-mt

Air with a dry bulb temperature $$t_{d1}$$ and a wet bulb temperature $$t_{w1}$$ is passed through a heater and then through an adiabatic cooler from which it emerges with dry and wet bulb temperatures of $$t_{d2}$$ and $$t_{w2}$$ respectively. Then

• always $$t_{w1} > t_{w2} \mbox { and } t_{d1} > t_{d2}$$

• always $$t_{w1} < t_{w2} \mbox { and } t_{d1} > t_{d2}$$

• always $$t_{w1} > t_{w2} \mbox { and } t_{d1} < t_{d2}$$

• $$t_{w1} < t_{w2} \mbox { and } t_{d1} \mbox { can be greater than, equal to or less than } t_{d2}$$

### GATE-CH-1990-5-v-mt-2mark

1990-5-v-mt

Lewis number = 1 signifies:

• $$\text {Pr} = \text {Sc}$$

• $$\text {Pr} = \text {Re}$$

• $$\text {Sc} = \text {Re}$$

• $$\text {Nu} = \text {Sh}$$

### GATE-CH-1998-2-13-mt-2mark

1998-2-13-mt

For the Air-Water system under ambient conditions, the adiabatic saturation temperature and the wet-bulb temperature are nearly equal, because

• water has a high latent heat of evaporation

• Lewis number is close to unity

• they are always equal under all circumstances

• solubility of the components of air in water is very small

[Index]

### GATE-CH-1998-2-8-mt-2mark

1998-2-8-mt

Air, initially at 101.3 kPa and 40$$^\circ$$C, and with a relative humidity of 50%, is cooled at constant pressure to 30$$^\circ$$C. The cooled air has

• A higher dew point

• A higher absolute (specific) humidity

• A higher relative humidity

• A higher wet bulb temperature

### GATE-CH-2001-1-13-mt-1mark

2001-1-13-mt

The Lewis relation for air-water humidification is given by ($$k_Y$$: mass transfer coefficient of moisture in air; $$h_G$$: heat transfer coefficient; $$C_S$$: heat capacity of vapor-gas mixture)

• $$\displaystyle \frac {h_G^2}{k_YC_S} = 1$$

• $$\displaystyle \frac {k_YC_S^2}{h_G} = 1$$

• $$\displaystyle \frac {h_G}{k_YC_S} = 1$$

• $$\displaystyle \frac {k_Y^2h_G}{C_S} = 1$$

### GATE-CH-2003-67-mt-2mark

2003-67-mt

The following plot gives the saturated humidity ($$H_e$$) versus Temperature ($$T$$).

Line joining $$(H_1,T_1)$$ and $$(H_2,T_2)$$ is the constant enthalpy line. Choose the correct one.

• $$T_1$$ - Dew point Temp; $$T_2$$ - Dry bulb Temp; $$T_3$$ - Wet bulp Temp.

• $$T_1$$ - Dew point Temp; $$T_2$$ - Wet bulb Temp; $$T_3$$ - Wet bulp Temp.

• $$T_1$$ - Wet bulb Temp; $$T_2$$ - Dry bulb Temp; $$T_3$$ - Dew point Temp.

• $$T_1$$ - Dry bulb Temp; $$T_2$$ - Wet bulb Temp; $$T_3$$ - Dew point Temp.

### GATE-CH-2016-13-mt-1mark

2016-13-mt

For what value of Lewis number, the wet-bulb temperature and adiabatic saturation temperature are nearly equal?

• 0.33

• 0.5

• 1

• 2

### GATE-MN-2013-41-mt-2mark

MN-2013-41-mt

Four psychrometric processes $$P$$, $$Q$$, $$R$$ and $$S$$ are shown in the psychrometric chart below.

These processes respectively represent

• dehumidification, humidification, sensible heating, sensible cooling

• sensible heating, humidification, dehumidification, sensible cooling

• dehumidification, sensible heating, sensible cooling, humidification

• humidification, sensible heating, dehumidification, sensible cooling

[Index]

### GATE-CH-XE-2008-G-8-mt-1mark

XE-2008-G-8-mt

If the moist air is heated at a constant pressure

• the specific humidity changes

• the relative humidity does not change

• the relative humidity decreases

• the relative humidity increases

### GATE-CH-XE-2009-E-2-mt-1mark

XE-2009-E-2-mt

• the relative humidity increases but the specific humidity remains constant

• both the relative humidity and the specific humidity remain constant

• both the relative humidity and the specific humidity increase

• the relative humidity decreases but the specific humidity increases

### GATE-CH-1994-3-c-mt-1mark

1994-3-c-mt

If an insoluble gas is passed through a volatile liquid placed in a perfectly insulated container, the temperature of the liquid will increase. (True/False)

• True
• False

### GATE-CH-1989-5-ii-e-f-mt-4mark

1989-5-ii-e-f-mt

Air is passed through a heater at constant pressure. The inlet and outlet conditions of the air are as follows:
Inlet:
Dry bulb temperature = 31.7$$^\circ$$C
Wet bulb temperature = 23.9$$^\circ$$C
Humidity = 30%
Outlet:
Dry bulb temperature = 70$$^\circ$$C
(i) The inlet air will have a dew point
{#1}

(ii) In the above problem, the air from the heater will have a humidity:
{#2}

### GATE-CH-2004-21-22-mt-2mark

2004-21-22-mt

An air-water vapor mixture has a dry bulb temperature of 60oC and a dew point temperature of 40oC. The total pressure is 101.3 kPa and the vapor pressures of water at 40oC and 60oC are 7.30 kPa and 19.91 kPa, respectively.

(i) The humidity of air sample expressed as kg of water vapor/kg of dry air is

{#1}

(ii) The wet bulb temperature $$T_w$$ for the above mixture would be

{#2}

[Index]

### GATE-CH-1996-2-17-mt-2mark

1996-2-17-mt

In a mixture of benzene vapor and nitrogen gas at a total pressure of 900 mm Hg, if the absolute humidity of benzene is 0.2 kg benzene/ kg nitrogen, the partial pressure of benzene in mm Hg is

• 180

• 60.3

• 720

• 200

### GATE-CH-1999-2-11-mt-2mark

1999-2-11-mt

If the specific heats of a gas and vapor are 0.2 kJ/kg.K and 1.5 kJ/kg.K respectively, and the humidity is 0.01, the humid heat in kJ/kg.K is

• 0.31

• 0.107

• 0.017

• 0.215

### GATE-CH-2007-29-mt-2mark

2007-29-mt

If the percent humidity of air (30oC, total pressure 100 kPa) is 24% and the saturation pressure of water vapor at that temperature is 4 kPa, the percent relative humidity and the absolute humidity of air are

• $$25.2, 0.0062$$

• $$25, 0.0035$$

• $$20.7, 0.0055$$

• $$18.2, 0.0035$$

### GATE-CH-2010-38-mt-2mark

2010-38-mt

At 25oC and 90% relative humidity, water evaporates from the surface of a lake at the rate of 1.0 kg/(m2.h). The relative humidity that will lead to an evaporation rate of 3.0 kg/(m2.h), with other conditions remaining the same, is

• 30%

• 50%

• 60%

• 70%

### GATE-CH-ME-2008-53-mt-2mark

ME-2008-53-mt

Moist air at a pressure of 100 kPa is compressed to 500 kPa and then cooled to 35oC in an aftercooler. The air at the entry to the aftercooler is unsaturated and becomes just saturated at the exit of the aftercooler. The saturation pressure of water at 35oC is 5.628 kPa. The partial pressure of water vapor (in kPa) in the moist air entering the compressor is closest to

• 0.57

• 1.13

• 2.26

• 4.52

[Index]

### GATE-CH-ME-2008-55-mt-2mark

ME-2008-55-mt

Air (at atmospheric pressure) at a dry bulb temperature of 40oC and wet bulb temperature of 20oC is humidified in an air washer operating with continuous water recirculation. The wet bulb depression (i.e., the difference between the dry and wet bulb temperatures) at the exit is 25% of that at the inlet. The dry bulb temperature at the exit of the air washer is closest to

• 10oC

• 20oC

• 25oC

• 30oC

### GATE-CH-ME-2010-42-mt-2mark

ME-2010-42-mt

A moist air sample has dry bulb temperature of 30oC and specific humidity of 11.5 g water vapor per kg dry air. Assume molecular weight of air as 28.93. If the saturation vapor pressure of water at 30oC is 4.24 kPa and the total pressure is 90 kPa, then the relative humidity (in %) of air sample is

• 50.5

• 38.5

• 56.5

• 68.5

### GATE-CH-ME-2012-A-31-mt-2mark

ME-2012-A-31-mt

A room contains 35 kg of dry air and 0.5 kg of water vapor. The total pressure and temperature of air in the room are 100 kPa and 25oC respectively. Given that the saturation pressure for water at 25oC is 3.17 kPa, the relative humidity of the air in the room is

• 67%

• 55%

• 83%

• 71%

### GATE-CH-XE-2010-E-16-mt-2mark

XE-2010-E-16-mt

Air-water vapor mixture having 100% relative humidity at 50oC is heated isobarically to 100oC in a closed system. If saturation pressure at 50oC is 12.352 kPa and at 100oC is 101.42 kPa, final relative humidity is

• 0%

• 8.2%

• 12.2%

• 100%

[Index]